I'm currently launching an asynchronous job with PHP to perform some tests. To make it work, I found on SO some tips, like the use of popen and start: $commande = "testu.bat"; $pid = popen('start /B ' . $commande, 'r'); $status = pclose($pid); The testu.bat's folder is in my user PATH. This script performs some task, and to control it's execution, it should generates a log file, but I never get it. Whereas if I just remove the /B option, it works fine and I get my log file. Did I miss something about background execution? How can I catch the error informations when it is running in the background?